In the distant future, humans have successfully colonized the planet Mars, and they are attempting to harvest resources deep beneath the planet's surface. However, we are not alone.. Recently, a large fleet of alien spaceships has appeared in deep space, and they are making their way toward Mars. Apparently, the aliens also have an interest in the red planet, and they'll stop at nothing until they've killed all the humans and destroyed their mining facilities. Your mission is to guard Mars from the invading aliens by destroying as many of their saucers as possible.